1. Technical Field
The present invention relates to a liquid ejecting apparatus, a drive circuit, and a head unit.
2. Related Art
An ink jet printer which uses a piezoelectric element (for example, a piezo element) and which prints an image or a text by ejecting ink is known. Piezoelectric elements are provided in correspondence with multiple nozzles in a head unit, each of the piezoelectric elements is driven in accordance with a drive signal, and thereby, a predetermined amount of ink (liquid) is ejected from the nozzle at a predetermined timing to form dots. The piezoelectric element is electrically a capacitive element like a capacitor, and needs to receive a sufficient current in order to operate the piezoelectric element of each nozzle.
Accordingly, a source drive signal which is a source signal of a drive signal is amplified by an amplification circuit, is supplied to a head unit as a drive signal, and drives the piezoelectric elements. An amplification circuit uses a method (linear amplification, refer to JP-A-2009-190287) of amplifying current for the source drive signal in class AB amplification or the like. However, since power consumption increases and energy efficiency decreases in the linear amplification, a class D amplification is also proposed in recent years (refer to JP-A-2010-114711). In short, in a class D amplification, a pulse width modulation or a pulse density modulation of the source drive signal is performed, a high-side transistor and a low-side transistor that are inserted in series between power supply voltages are switched in accordance with the modulated signal, an output signal which is generated by the switching is filtered by a low pass filter, and thus, the source drive signal is amplified.
Energy efficiency of a class D amplification method is higher than that of a linear amplification method, however, power which is consumed by a low pass filter cannot be ignored, and thus, there is room for improvement in terms of reducing power consumption.